Imports System.ServiceModel
Imports System.Threading
Imports System.Xml
Imports DigitalData.Modules.Base
Imports DigitalData.Modules.EDMI.API.EDMIServiceReference
Imports DigitalData.Modules.Logging

Public Class Channel
    Inherits BaseClass

    Private ReadOnly ChannelFactory As ChannelFactory(Of IEDMIServiceChannel)

    Public Event Reconnect As EventHandler
    ' Verbindungszähler
    Private Shared _ActiveConnections As Integer = 0
    Public Shared ReadOnly Property ActiveConnections As Integer
        Get
            Return _ActiveConnections
        End Get
    End Property

    Public Shared Function GetBinding(Optional AuthenticationMode As TcpClientCredentialType = TcpClientCredentialType.Windows) As NetTcpBinding
        Return New NetTcpBinding() With {
        .MaxReceivedMessageSize = Constants.ChannelSettings.MAX_RECEIVED_MESSAGE_SIZE,
        .MaxBufferSize = Constants.ChannelSettings.MAX_BUFFER_SIZE,
        .MaxBufferPoolSize = Constants.ChannelSettings.MAX_BUFFER_POOL_SIZE,
        .ListenBacklog = Constants.ChannelSettings.MAX_CONNECTIONS,
        .MaxConnections = Constants.ChannelSettings.MAX_CONNECTIONS,
        .TransferMode = TransferMode.Streamed,
        .SendTimeout = TimeSpan.FromSeconds(30),      ' ← War: 5min → Schnellere Fehlererkennung
        .ReceiveTimeout = TimeSpan.FromMinutes(10),   ' Keepalive < Firewall-Timeout (3600s) ✓
        .OpenTimeout = TimeSpan.FromSeconds(30),      ' ← Neu: Verbindungsaufbau begrenzen
        .CloseTimeout = TimeSpan.FromSeconds(30),
        .Security = New NetTcpSecurity() With {
            .Mode = SecurityMode.Transport,
            .Transport = New TcpTransportSecurity() With {
                .ClientCredentialType = AuthenticationMode
            }
        },
        .ReaderQuotas = New XmlDictionaryReaderQuotas() With {
            .MaxArrayLength = Constants.ChannelSettings.MAX_ARRAY_LENGTH,
            .MaxStringContentLength = Constants.ChannelSettings.MAX_STRING_CONTENT_LENGTH
        }
    }
    End Function

    Public Sub New(pLogConfig As LogConfig, pServerAddress As ServerAddressStruct)
        MyBase.New(pLogConfig)
        ChannelFactory = GetChannelFactory(pServerAddress)
    End Sub
    ''' <summary>
    ''' Closes a channel gracefully, falls back to Abort on error
    ''' </summary>
    Public Shared Sub CloseChannel(pChannel As IEDMIServiceChannel)
        If pChannel Is Nothing Then Return

        Try
            If pChannel.State = CommunicationState.Opened Then
                pChannel.Close()
            ElseIf pChannel.State = CommunicationState.Faulted OrElse
                   pChannel.State = CommunicationState.Closing Then
                pChannel.Abort()
            End If
            ' CommunicationState.Created / Closed → nichts tun, Zähler nicht betroffen
        Catch ex As Exception
            Try
                pChannel.Abort()
            Catch
                ' Ignore
            End Try
        End Try
    End Sub
    ''' <summary>
    ''' Creates a channel and adds a Faulted-Handler
    ''' </summary>
    ''' <returns>A channel object</returns>
    Public Function GetChannel() As IEDMIServiceChannel
        Try
            Logger.Debug("Creating channel.")
            Dim oChannel = ChannelFactory.CreateChannel()

            ' Verbindung zählen beim Öffnen
            AddHandler oChannel.Opened, Sub()
                                            Dim oCount = Interlocked.Increment(_ActiveConnections)
                                            Logger.Debug("Channel opened. Active connections: [{0}]", oCount)
                                        End Sub

            ' Verbindung abziehen beim Schließen oder Fehler
            AddHandler oChannel.Closed, Sub()
                                            Dim oCount = Interlocked.Decrement(_ActiveConnections)
                                            Logger.Debug("Channel closed. Active connections: [{0}]", oCount)
                                        End Sub

            AddHandler oChannel.Faulted, Sub()
                                             Dim oCount = Interlocked.Decrement(_ActiveConnections)
                                             Logger.Warn("Channel faulted. Active connections: [{0}]", oCount)
                                             RaiseEvent Reconnect(Me, Nothing)
                                         End Sub

            Logger.Debug("Channel created. State=[{0}]", oChannel.State)
            Return oChannel
        Catch ex As Exception
            Logger.Error(ex)
            Throw
        End Try
    End Function

    Private Function GetChannelFactory(pServerAddress As ServerAddressStruct) As ChannelFactory(Of IEDMIServiceChannel)
        Dim oBinding = GetBinding()
        Dim oAddress = New EndpointAddress($"net.tcp://{pServerAddress.Host}:{pServerAddress.Port}/DigitalData/Services/Main")
        Logger.Debug("Creating ChannelFactory with Binding: SendTimeout=[{0}], ReceiveTimeout=[{1}], MaxConnections=[{2}], MaxBufferSize=[{3}], TransferMode=[{4}]",
            oBinding.SendTimeout,
            oBinding.ReceiveTimeout,
            oBinding.MaxConnections,
            oBinding.MaxBufferSize,
            oBinding.TransferMode)
        Dim oFactory = New ChannelFactory(Of IEDMIServiceChannel)(oBinding, oAddress)
        Return oFactory
    End Function

End Class